1. Field of the Invention
The present invention relates to public cordless telephone systems which comprise a base unit and a branch unit connected to the base unit through a radio link to be used by many unspecified persons and, more particularly, to a public cordless telephone system which has a user charging function, a function of managing the charged state of a battery provided in a branch unit and a function of preventing the branch unit from being stolen.
2. Description of the Related Art
In general, a so-called public telephone system to be used by many unspecified persons has been widely known. This public telephone system, as shown in FIG. 22, comprises a telephone main unit 3 and a handset 5 connected to the telephone main unit 3 through a coiled cord 4. The telephone main unit 3 is connected to a public line 1 which is connected to a public line network (not shown) and has an A.C. plug 2 provided to supply commercial power to the main unit 3 therethrough.
However, such a prior art telephone system is limited in its use by the extendible maximum length of the coiled cord 4, because of the physical interconnection between the telephone main unit 3 and the handset 5 to which the user's ear and mouth are positioned. For example, when the telephone main unit 3 is installed at a positional level to allow users to use the telephone while standing, e.g., at a predetermined height from the ground level, users can comfortably use the telephone while standing. However, when it is desired for a user to use the telephone while taking a different pose other than the above standing one, the limited maximum length of the coiled cord 4 imposes restrictions to the telephone's use, preventing the user from moving about freely.
Very recently, various uses of the public telephone system have been considered. In some applications, it is demanded that the public telephone be used at an arbitrary position in a given space.
For example, when the public telephone system is installed in a restaurant or a hotel lobby having a certain area, the conventional public telephone cannot be used at any place but only at one specific limited location, which is highly inconvenient for users. In this case, if the user could use the telephone while sitting in a chair away from the location where the telephone is installed or if the user could use it while sitting in a sofa or couch located close to the telephone installation location, it would be very convenient for the user. However, since the prior art public telephone system is limited in use by the specific length of the coiled cord 4 between the telephone main unit 3 and the handset 5, it is impossible to use the telephone in such a manner.